Products installed on top of a subfloor and under a floor treatment that aid in the floor treatment's installation are known in the art. Often, it is desirable to prevent a floor treatment from absorbing moisture that seeps up through a subfloor that may cause a floor treatment to degrade or swell, potentially causing the flooring to buckle to lift away from the subfloor, causing, for example, premature glue-joint failure. A problem associated with prior art underlays applied between the floor treatment arid subfloor is that their installation tends to be overly complicated and difficult. One example of a known underlay product uses a layer of low density thermoplastic foam applied over a subfloor. This foam is generally porous and allows moisture to seep up through the foam and contact the floor treatment, which may thereby damage the floor treatment in the manner mentioned above. In order to prevent this problem, a second layer of thermoplastic film must be installed over the layer of foam to act as a moisture barrier. The foam layer and the film layer tend to shift and fold during installation and must be adhesively tacked both together and to the subfloor so that shifting or folding is minimized when laying the floor treatment. Also, the low density foam used in this system allows vertical impacts, e.g., foot falls, to resonate and be amplified through the floor treatment where the treatment is laminate wood flooring, for example, resulting in an undesirably loud floor installation.
Another underlay system uses a compressed rigid fiberboard in conjunction with a thermoplastic layer. The fiberboard is directly applied to a subfloor in small sheets. Small sheets of the rigid fiberboard installed side by side result in a large number of joints in the assembled underlay which must be sealed. The large number of joints to be sealed increases the probability of premature joint failure from repeated foot falls to the joints since the rigid fiberboard sheets tend not to give but, rather, to separate relative to each other. As with the above example, in order to make this underlay moisture impermeable, a thermoplastic film must be adhesively tacked to the fiberboard. The fiberboard and film assembly degrades and literally falls apart over time due to repeated vertical impacts to the floor treatment, i.e., walking over the floor. Once the fiberboard fails, a soft spot is created under the floor treatment which leads to an uneven surface and, ultimately, failure of the floor treatment above the degraded underlay region. This construction is also susceptible to amplifying the sound of foot falls.
Certain foams are unsuitable for use as flooring underlay. For instance, a polyethylene foam is a closed cell foam, the closed cells being under slightly positive pressure from the physical blowing agent captured therein, formed during the foaming process. The closed cells are what give the foamed product its resiliency and much of its thickness. If the foam cells are ruptured, the foam loses its resiliency and thickness and creates a dead spot in the foam that leads to degradation of the floor treatment, and increased noise as mentioned above.